This invention relates to cooking apparatus and methods, and, more particularly, to a deep fat fryer for the frying of foods through the uniform transfer of heat over a large area to a cooking medium in which the food is immersed.
The cooking apparatus that are employed to fry foods are legion in number and vary in complexity from the simple, as typified by U.S. Pat. No. 3,722,498 issued on Mar. 27, 1973 to Kimbrough, to the more complex, as represented by U.S. Pat. No. 4,913,041 issued on Apr. 3, 1990 to Taber et al. The object of all prior art deep fat fryers is to constantly transfer heat to the cooking medium, such as oil or shortening (and generally referred to as “cooking oil” or “oil” in the discussion that follows), so as to raise and maintain the temperature of the cooking oil at a level sufficient to fry the selected food and to cook the food to the desired consistency and texture. However, the nature of the cooking oil is such that, over a period of time, it ultimately degrades and deteriorates. This deterioration is partly due to chemical changes that occur in the fats and oils through hydrolization, oxidation and new carbon—carbon linkages. Such deterioration in the cooking oil itself ultimately requires replacement with fresh oil.
Additionally, food particles carbonize due to the high cooking heat in proximity to the heating elements, resulting in a collection of fine debris within the oil itself over a period of use. For example, many foods are encased in batters containing both free and bound sugars and amino acids. During the browning process, the free-floating batter particles, often referred to as “cracklings,” become increasingly dark, and a bitterness can be detected through tasting. Furthermore, the cooking oil itself becomes dark in color. Ultimately, the flavor of the food is detrimentally affected. One common way to reduce the amount of food particles in the cooking oil is to periodically filter the oil. While filtering may help address the problem, it clearly represents both capital and labor expenses. Operators frequently find it more economical to replace a portion of the used oil with fresh oil and dispose of the used oil. However, it still remains a goal of those skilled in the art to reduce the turnover in oil usage by increasing the longevity of use of the oil.
As alluded to above, the degradation and deterioration of the cooking oil over a period of time is primarily related to the high heat needed to heat the cooking oil to the desired operating temperature. That is, the cooking oil is generally heated by elements immersed within the oil itself. Because the cooking oil is an inefficient medium for transferring heat, i.e., has a low transfer of heat coefficient, it is necessary that the heating elements operate at temperatures significantly higher than the average operating temperature of the oil. Thus, the oil directly adjacent the elements is at a much higher temperature than oil a short distance away. More often than not, the temperature of the heating elements exceeds the “smoke point” of the cooking oil itself. To minimize degradation and deterioration, prior art deep fat fryers generally provide for structural designs and volume capacities that promote the natural circulation within the frying tank. Natural circulation, i.e., circulation without pumps and the like, requires that the body of the cooking oil be sufficiently large to allow oil circulation from changes in relative densities due to heating and cooling. Thus, in most prior art deep fat fryers, the body of oil used at any one time is considerably larger than is actually required to cook the food. This clearly requires tank volumes to be sufficiently large to accommodate the quantity of oil appropriate to minimize rapid oil degradation. Unfortunately, space in most cooking facilities is at a premium.
Still another problem associated with prior art deep fat fryers is the significant heat loss of the cooking oil through the external walls. Heating inefficiencies require longer sustained heating by the elements themselves and results in greater oil degradation. Thus, some of the prior art fryers attempt to address heat loss inefficiencies.
Additionally, many improvements in the state of the art have occurred as a direct result of attempts to allay handling and cleaning problems associated with deep fat fryers. Handling of the fryer at the high operating temperatures is awkward as a consequence of the ever present danger of burn injuries to personnel. Reducing the frequency of handling clearly would lower the probability of injury. Cleaning of the fryer also poses problems due to the collection of carbonized particles at the bottom of the fryer tank and on the heating elements themselves. In many fryers, the heating elements are removable or pivotable to allow personnel to scour all internal wall surfaces. Drain valves are often located at the bottoms of the tanks to permit drainage of the used and dirty oil. Too frequently, however, the drains themselves become plugged with debris.
An example of a deep fat fryer developed to reduce the localized heating effect often found in fryers and to increase the efficiency of heat transfer is U.S. Pat. No. 4,690,127 issued on Sep. 1, 1987 to Sank. This patent describes the use of a catalytic heater having an elongated hollow oval structure adapted to immersed in the cooking oil. Aside from the clear fact that the heat transfer within the oil is largely unaffected, the volume occupied by the catalytic heater is significant.
The aforementioned U.S. Pat. No. 4,913,041 represents still another attempt to increase the efficiency of heat transfer by eliminating some of the heat loss through the external walls of the fryer tank and to facilitate the cleaning of the fryer. The fryer tank itself is provided with a plurality of wells extending from the bottom of the tank. Oil within the wells is heated by the passage of hot gas along horizontal passageways, thus providing a larger surface area for heat transfer to the oil as compared to tubular heating elements immersed in the oil.
Other attempts at improvements in heat transfer efficiency have been the use of gas infrared burners (porous ceramic plates) butted to the walls of the fry tank or suspended in cylinders at the bottom of the fry tank. Additionally, convection fryers have been developed in which hot oil is pumped continuously through the fry tank.
It is therefore an object of the present invention to provide a deep fat fryer that improves the efficiency of transfer of heat from the heating elements to the cooking oil.
It is another object of the present invention to provide an improved deep fat fryer that facilitates cleaning and handling of the fryer.
It is still another object of the present invention to provide an improved deep fat fryer that reduces the amount of oil needed for cooking.
It is yet another object of the present invention to provide an improved deep fat fryer apparatus that lowers the rate of cooking oil degradation and deterioration during use.
These and other objects and advantages of the present invention will become apparent upon a reading of the following description.